I my experience, fixed wing stabilisers (totally unnecessary in 99% of applications) are switchable given you, as the controller, decides what applies.
Apart from that, if you consider it "so important" then why muck with it in the first place.
The resistor in that case will be in series with the LED/LEDs so their voltage drop must be subtracted first.
i.e. if you have 2 red LEDs in series with your resistor, you must first subtract 2 x 1.7v (or there abouts) first.
Remainder is the voltage that will appear across the resistor.
If 12v...
Do you have either the manual or a link to your model..??
NiCads and Nickel metal are nominal 1.2v, nothing you can do to change that.
I'd be very surprised if an rc transmitter or receiver would not operate on 1.2v rechargable cells.
Servos and receiver will normally work fine down to at...